No I don't think thats the case at all.
I think an aggressive fish is aggressive by nature or by circumstance. I don't think a steelhead has ever one time throughout the annals of history refused one fly then turn around and struck another fly for any reason that humans will ever understand. No steelhead ever saw 1/0 skunk then turned around and grabbed a 1/0 green butt skunk because of the green butt. It ain't never happened! PERIOD!
If you catch a fish behind somone in the run it's because their fly was unseen by the fish or something in the attitude of the fish changed between seeing his fly and yours or the presentation was sufficiently different.
I do not believe that subtle changes in pattern color or size make a bit of difference. The only time it makes sence to fish through a run more than once is to fish a radically different fly. or presentation or unless you believe for some reason the fish may more willing to respond. For instance if it suddenly became overcast or the sun go off the water or whatever condition you think may make a fish inclined to bite.
This is of course just my opinion..
I grew up on the Washougal and did A LOT!!!! of sight fishing. I have spent hours throwing different patterns to the same fish. here are some things I learned. or at least things I believe that I learned enough to form this opinion. These suppositions have been verified by a year of fishing the Umpqua and subsequent week long trips after that. In fact it has been the case everywhere I have fished.
1. nearly every steelhead I have caught took the fly on the very first presentation the fly was visible to the fish.
2 nearly every steelhead I have ever caught has come through the first pass through a run
3. visible fish in the vast majority of cases grow weary the more times they see a fly and after a while spook from thier lie entirely
4. Ever visible steelhead I have caught that didn't respond to the first fly I put over them didn't respond to any similar pattern and ONLY responded to radically different approaches.
Based on my observations
you can argue the percentages if you want. thats not my point.
1. nearly every steelhead will ignore every fly 90% of the time. That means at any given time we are fishing for 10% of the entire population.
2. Of that 10%, 10% will be in holding water that is actually fly water. particularly true for winter runs.
3. of that very small % of the entire run how many of thoes fish are in the run you are fishing??
4 of that even smaller % very few of them will be selective to size, color, or style.
Here is my point. There are very few fish willing to take a fly, and most of thoes are going to grab the first fly they see in their comfortable strike zone. There fore your best bet to catch a fish is to make as many good first presentations as you can in the course of a day.
On the other hand.. STEELHEAD ARE STUPID!!! WE ARE WAY WAY WAY WAY WAY OVERTHINKING THIS!!!
Pick a fly that you like and makes sence to you for the conditions and put it in front of as many fish as you can as best you can. That is ALL there is to steelhead fishing. Everything else is BS.. IMHO.
I could have made a more simplistic answer and just say. If you pick a 1/0 skunk and fish only that 24/7/265 you'll catch as many or more steelhead than anyone else on the planet.
Steelhead are the most noble fish that swim in the water but they are dumb. You can tell that just by the fact that they take the flies I tie..
Also keep in mind this is just my BS. nothing more